[47.01] Evidence for Reactor Anti-Neutrino Disappearance at KamLAND

J.M. Goldman (Tohoku University), KamLAND Collaboration

KamLAND, the first terrestrial experiment with direct
sensitivity to the Large Mixing Angle (LMA) solution to the
solar neutrino problem, has measured the flux of electron
anti-neutrinos produced by distant (flux-weighted baseline
of approximately 180 km) nuclear reactors. Fewer electron
anti-neutrino events are observed in this measurement than
are predicted by the Standard Solar Model and the
non-oscillation hypothesis at the 99.95% C.L. Using data
corresponding to a period of 162 ton-years, KamLAND has
found the ratio of the measured number of anti-neutrino
events to the expected number of anti-neutrino events to be
equal to 0.611±0.085(stat)±0.041(syst) for
anti-neutrino energies greater than 3.4 MeV. With the
assumption of CPT invariance and a two-flavor oscillation
formalism, this measurement excludes all solutions to the
solar neutrino problem other than LMA.